Topographic Modeling

Sense the Invisible

Beyond RGB

Measure and combine radiation from multiple spectral bands to perceive what the eye cannot.

Types of Drones

Fixed-Wing UAVs

Fixed-wing UAVs use their airplane-like design to fly larger regions of interest over shorter periods of time, at the expense of higher purchase costs and the need for clear take-off and landing runways. They also often ship with commercial software for processing imagery.

Quadcopters

Quadcopters/rotorcraft can be easily switched between stable manual controls for preliminary surveying and fully-autonomous control for orthomosaic generation or specialized cinematography. They are also more affordable, and can be launched or landed from anywhere.

Motivations from Ag and Remote Sensing

“Decentralization has, not only an administrative value, but also a civic dimension, since it increases the opportunities for citizens to take interest in public affairs; it makes them get accustomed to using freedom.”

— Alexis de Tocqueville

Drones have been popularized in the media for their military and tourism applications. However, we are primarily interested in their potential to unlock critical barriers in collecting agroecological data.

Agriculture is a big data problem requiring modeling of complex natural processes with untold degrees of freedom. However, despite its importance, agriculture lags far behind many fields in terms of the quantity of data being collected, particularly in regions such as Sub-Saharan Africa or Southeast Asia. The challenges of collecting agricultural data are manifold, and include financial constraints, poor infrastructure, and the logistics of coordinating large-scale ground operations.

In the absence of having boots on the ground, researchers often rely on satellite imagery, which has been extremely useful for macroscale studies. However, satellite imagery also has several drawbacks, such as

insufficient spatial resolution to discern plot-level features, such as types of crops/trees grown along with heights and health variations,

limited temporal resolution for many longitudinal studies, such as tracking monthly deforestation in a region for a decade, and

limited access to raw data, locked behind expensive paywalls managed by large corporations, often with ties to the defense industry.

The rise of drones brings with it the opportunity for both higher spatial-temporal resolutions and the decentralization of power. While geosynchronous satellites fly 36,000 km above the earth, drones can fly much closer to the ground (e.g., 25-150 m), circumventing cloud cover problems and achieving spatial resolutions on the order of 5 cm, unattainable by satellites. Frequency of imaging is also no longer constrained by satellite schedules, as we are now only constrained by our own logistical capabilities on the ground. By taking overlapping photos, the parallax effect can be used to construct up-to-date digital elevation models. And lastly, drones can be readily equipped with multispectral sensors to measure non-visible vegetation indices.

Challenges of Using Drones

The aforementioned benefits of UAVs are very promising, but they cannot be reaped by citizen scientists unless more engineering and research is executed to reduce their costs, simplify their operation, and bring clarification to the plethora of options available today. Some of the key drawbacks to making drones practical for scientific studies include:

the high cost of purchase and difficulty of conducting repairs, particularly in developing countries,

complexity of flight operations, and

financial costs and lack of direction about where to store and process the large datasets resulting from UAV flights.

Solutions

Inspired by the many difficulties that come with operating drones in SSA, QED has been building solutions to bypass all of the aforementioned problems.

Automated Quadcopter Flight

Using quadcopters that are 10x-30x cheaper than COTS fixed-wing drones, we can generate data products of identical quality. Our own Android app named AutoDrone allows users to easily command quadcopters to follow orthomosaic flight paths at the push of a button, and even chain together multiple flights to compensate for shorter battery times.

Customization and Repairability

We have built custom-designed quadcopters out of basic components, resulting in designs that are easier to repair when small components break, and which can also be assembled from individually shipped constituents to bypass import regulations.

We have also experimented with quadcopters that are modified to carry sensors that do not normally ship with the product, as illustrated in the rightmost images above, where an NDVI sensor siphons power from the internal mainboard.

Post-Processing, Storage, and Visualization

We have built custom-designed quadcopters out of basic components, resulting in designs that are easier to repair when small components break, and which can also be assembled from individually shipped constituents to bypass import regulations.

Processing and storage is handled by our Hive platform, which takes the guesswork out of organizing metadata organization, provides scalable storage for users, asynchronously handles post-processing of imagery, and produces visualizations of orthomosaics in the browser.

Geotagging and Classification

Drone imagery can be re-routed into Geosurvey for systematic crowdsourced analysis, leading to automated identification of agroecological variables such as carbon storage, erosion, and stand counts.